In the manufacture of various types of tissue products such as facial tissue, bath tissue, paper towels and the like, the dried tissue web or sheet coming off of the tissue machine is initially wound into a parent roll and temporarily stored for further processing. Sometime thereafter, the parent roll is unwound and the sheet is converted into a final product form.
In winding the tissue web into a large parent roll, it is vital that the roll be wound in a manner which prevents major defects in the roll and which permits efficient conversion of the roll into the final product, whether it be boxes of facial tissue sheets, rolls of bath tissue, rolls of embossed paper towels, and the like. Ideally, the parent roll has an essentially cylindrical form, with a smooth cylindrical major surface and two smooth, flat, and parallel end surfaces. The cylindrical major surface and the end surfaces should be free of ripples, bumps, waviness, eccentricity, wrinkles, etc., or, in other words, the roll should be xe2x80x9cdimensionally correct.xe2x80x9d Likewise, the form of the parent roll must be stable, so that it does not depart from its cylindrical shape during storage or routine handling, or, in other words, the parent roll should be xe2x80x9cdimensionally stable.xe2x80x9d Defects can force entire parent rolls to be scrapped if they are rendered unsuitable for high speed conversion.
New tissue reels and winders having an endless belt, such as that disclosed in U.S. Pat. No. 5,901,918 issued May 11, 1999 to Klerelid et al. and herein incorporated by reference, are found effective in the winding of tissue webs having a bulk of 9 cubic centimeters per gram or higher and a high level of softness, as characterized, for example, by an MD Max Slope of about 10 kilograms or less per 3 inches of sample width. Such reels and winding methods can be used to produce dimensionally correct and dimensionally stable parent rolls of such soft tissue webs having diameters on the order of 70 to 150 inches. Such parent rolls are disclosed and claimed in U.S. Pat. No. 5,944,273 issued Aug. 31, 1999 to Lin et al. and herein incorporated by reference.
However, as the winding speeds of such reels are increased to production rates exceeding 3,600 fpm, effectuating an efficient turn-up and maintaining sheet control of the tissue web on the endless belt can be challenging. Therefore there is a need for a method of winding soft, bulky tissue sheets in which the variability in sheet bulk, caliper, machine direction stretch, and/or basis weight is minimized, while still maintaining parent roll characteristics that are favorable to manufacturing and converting operations. There is also a need for such a reel to operate at machine speeds in excess of 3,600 fpm while maintaining sheet control and a high level of turn-up efficiency in order to manufacture such tissue webs cost effectively.
These and other needs are met by the apparatus and method according to the present invention which includes an endless flexible member having a winding region for engaging the web of tissue paper against a reel spool and a web transport region. The endless flexible member thus forms a xe2x80x9csoft nipxe2x80x9d with the reel spool. A deflection sensor is mounted adjacent to the flexible member for measuring the amount of deflection of the flexible member. The amount of deflection is related to the pressure at the nip point and, by moving the reel spool and flexible member away from each other as the diameter of the paper roll increases, the pressure can be controlled at a desired level. Accordingly, the tissue winding parameters are greatly improved and the differences in properties of an unwound paper roll can be minimized.
To maintain sheet control and to improve turn-up efficiency, the endless flexible member is air permeable. A means for pressure reduction, such as a coanda vacuum box, is located along at least a portion of the endless flexible member in the winding region. A reduced air pressure is generated on an inside surface of the flexible member such that the tissue web disposed on an outside surface of the flexible member is brought into contact with the flexible member. Accordingly, during a turn-up improved efficiency results due to the control of the tissue web, particularly of the loose bits and scrap material present when the web tears as the turn-up progresses. In addition, during parent roll winding, less skating and weaving of the tissue web from the improved contact with the flexible member results in a parent roll having a more uniform cylindrical shape.
Hence in one aspect the invention resides in, an apparatus for winding a web into a roll including a rotatably mounted reel spool; an air permeable endless flexible member mounted for rotation along a predetermined path of travel having a winding region and a web transport region, and the winding region is positioned adjacent to the reel spool; a sensor measuring a deflection of the flexible member from the predetermined path of travel; an actuator for positioning the reel spool and the flexible member relative to each other to vary the deflection of the flexible member; a controller connected to the sensor and the actuator for controlling the deflection of the flexible member as the roll increases in diameter; and a means for pressure reduction located along at least a portion of the predetermined path of travel in the winding region.
In another aspect the invention resides in, an apparatus for winding a web of paper material into a roll including a rotatably mounted reel spool; a drive motor for rotating the reel spool and winding a paper web thereon to create a parent roll of increasing diameter; an air permeable endless flexible belt having an inside surface and an outside surface supported for rotation around a plurality of support rolls defining a predetermined path of travel, the predetermined path of travel having a winding region including a free span and a pair of support rolls, and a web transport region preceding the winding region, the paper web residing on the outside surface and positioned adjacent the reel spool engaging the reel spool during winding such that the free span is deflected from the predetermined path of travel by the paper web wound on the reel spool; a deflection sensor mounted within the belt measuring a deflection of the inside surface from the predetermined path of travel; an actuator for positioning the reel spool and the belt relative to each other to vary the deflection of the inside surface; a controller connected to the deflection sensor and the actuator for controlling the deflection of the inside surface as the parent roll diameter increases; and a means for pressure reduction located along at least a portion of the inside surface in the winding region.
In another aspect the invention resides in a method of winding a web to form a roll comprising the steps of: engaging an endless flexible member against a reel spool creating a nip such that the flexible member is deflected from a predetermined path of travel, the endless flexible member having a winding region, a web transport region, and an inside surface; rotating the reel spool; rotating the endless flexible member; advancing the web into the nip and directing the web around the reel spool to form a roll of increasing diameter; sensing the amount of deflection of the flexible member by the roll as the diameter of the roll increases; moving at least one of the reel spool and the flexible member in response to the sensing step to vary the amount of deflection of the flexible member; and reducing the pressure along at least a portion of the inside surface within the winding region.